The dendritic morphology of pyramidal neurons in the rat hippocampal CA3 area. II. Effects of gender and the environment.

Sex differences in the dendritic structure of hippocampal CA3 pyramidal neurons were studied in Golgi-stained tissue from hooded rats that had been raised in either a relatively complex or an isolated environment from weaning for one month. Pyramidal neurons were sampled from both the short-shaft and long-shaft neuron categories as described by Fitch et al. The pattern of sex differences varies in different parts of the apical dendritic tree. In the apical tree proximal to the soma, females had more dendritic material than males. This pattern was attributable to the sex differences in the short-shaft neurons of rats from the more complex environment. The direction of sex differences was reversed in the distal apical dendritic tree where males had more dendritic material than females. As in the proximal dendritic tree, this pattern of sex differences stemmed from the short-shaft neurons of rats from the more complex environment. There were no sex differences in the basilar dendritic tree. Thus sex differences in the pyramidal neurons of hippocampal area CA3 vary with the portion of the dendritic tree examined, the type of pyramidal neuron, and the rearing environment of the animal.